Home' Trinidad and Tobago Guardian : September 25th 2014 Contents SEPTEMBER 2014 • WEEK FOUR www.guardian.co.tt BUSINESS GUARDIAN
NEWS | BG15
As we seek to assure appropriate seis-
mically resilient communities there
is a particular hurdle to be over-
come. This concerns a critical lack
of awareness of what a building
code provides to property owners
and end-users in terms of losses. Appropriate seis-
mically resilient communities are those that implement
the latest scientific and technological advances in
the design and construction of physical infrastructure
in consideration of all the costs involved. Such
advances are passed on to society via the latest
building codes and any property owner or occupant
should be keen to know of same so as to maximise
safety and minimise costs. Hence, there is a vital role
to be played by property owners, end-users and the
The following statement is invariably shocking
when first heard and there seems to be no easy way
to introduce it. When the earthquake a building is
designed to resist occurs, there will always be losses
in terms of casualties, damage, and functionality for
a period of time (that is, downtime).
Therefore, for any town, there will always be a risk
that medical and other services or resources required
for recovery operations, will be overwhelmed. However,
it is at first believed by property owners or end-users
that not only should there be no losses, but that this
is the engineer s job.
Engineers truly wish this were possible, but it is
not possible due to the way nature operates. The
issue is this: when a structure vibrates due to the
vibration of the ground, the damage imparted to the
structure depends on the sum of the forces at each
instant of time during the vibration, and not just the
maximum force, and it is literally impossible to predict
what that will be (viz. the technical term is "record-
So when your engineer designs your structure for
a certain level of force, there is always a chance that
the actual force, hence damage will be higher. This
is often observed after an earthquake---say there are
ten identical houses on a street, one will collapse and
another will not have a single crack.
This implies that expected losses are to be con-
sidered by the populace who must then decide if
they are acceptable to society.
Therefore, acceptable losses represent the basic
safety, in monetary terms, that should be built into
the structure. Such acceptable losses also represent
a benchmark that can then be made part of local
design and construction policy.
This benchmark represents basic safety but, of
course, a property owner or end-user can specify a
different but lower level of acceptable loss and instruct
the engineer to design the structure to suit. That is,
the engineer is instructed on the maximum number
of casualties, the maximum repair cost, and maximum
downtime for the building. The owner specifying the
acceptable losses, and the engineer providing a struc-
ture to suit these losses, are the core of what is called
"performance-based design" and is the latest approach
to safety under earthquakes.
At this point, it is prudent to provide examples of
the extent of losses associated with basic safety pro-
vided by the latest building codes applied to an earth-
quake prone region sufficiently similar to T&T. For
example, the expected number of casualties due to
collapse of concrete buildings or its components are
50 to 100 people per 1,000 buildings. This is for
buildings designed and built to code.
If the buildings are not designed and built to code,
the number of casualties is about ten times higher.
The economic cost due to building damage is about
20 to 30 per cent of the replacement value of the
building and roughly 15 times the cost associated
with the casualties for buildings built to code.
Note that these losses are the expected losses given
the latest building codes, but the question remains
open as to the acceptability of these and other specific
levels of losses for T&T. As would be expected, a
higher level of safety, hence lower losses requires
providing more robust buildings.
Some may consider it reasonable that a more devel-
oped country should have lower acceptable losses
than a less developed country for its basic safety pro-
As a first step, the citizenry needs to appreciate
the concept of inevitable losses, even if the building
is designed and built to code. Then, in order to provide
a policy on basic safety in the form of acceptable
losses, public consultation is needed. The aforemen-
tioned expected losses are for the region of southern
California, United States.
A decision was made by the Association of Pro-
fessional Engineers of T&T in 1978 to adopt the
building codes in use in California for local application.
To simplify the decision-making process, the question
can be phrased in terms of what per cent of this
benchmark should be adopted for local application
A level below 100 per cent means setting a level of
basic safety for T&T that is higher than that for Cal-
ifornia and a level above 100 per cent means a lower
level of safety. Ultimately, a range of percentages can
be presented for selecting one, say 80, 90, 100, 110,
120, 130 per cent.
It is envisaged that representatives of residential
districts, commercial, and governmental properties,
will make the final decision.
To facilitate the process, an Internet-based ques-
tionnaire can be readily prepared and activated for
a certain period and when that period elapses, the
responses are analysed and the results presented for
discussion by these representatives, other stakeholders,
and authorities responsible for policy-making. Such
input will eventually be vital for the local building
code development personnel, practicing engineers,
disaster managers, and development economists.
The author hopes that these opportunities will be
fully utilised as we seek to maximise public safety
and optimise the use of the country s resources.
Former chairman of the BOETT/APETT/TTBS
Structures Codes Committee
represent the basic
safety, in monetary
terms, that should be
built into the structure.
Such acceptable losses
also represent a
benchmark that can then
be made part of local
design and construction
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